The terrestrial planets are made almost entirely of elements ...

[stevenposner]

The terrestrial planets are made almost entirely of elements heavier than hydrogen and helium. According to modern science, where did these elements come from?
 
  A) They were produced by gravity in the solar nebula as it collapsed.
  B) They were produced by stars that lived and died before our solar system was born.
  C) They have been present in the universe since its birth.
  D) They were made by chemical reactions in interstellar gas.

Question 2

Briefly describe the evidence suggesting that a 10-km asteroid or comet hit Earth at the time of the dinosaur extinction.
 
  What will be an ideal response?

[rnehls]

Answer to Question 1

B

Answer to Question 2

A layer of clay at this level in the sediments is rich in materials found in asteroids but not normally found on Earth's surface. A crater off the Yucatan peninsula dates to the right time and is the right size.

[stevenposner]

Thanks

[rnehls]

Welcome